Nitrous Oxide Emissions from a Coal Mine Land Reclaimed with Stabilized Manure

Mine-soil treatment using stabilized manure rapidly sequesters large quantities of organic carbon and nutrients. However, the nutrient-rich soil conditions may become highly conducive for production and emission of N₂O. We examined this possibility in a Pennsylvania coal mine restored using poultry manure stabilized in two forms: composted (Comp) or mixed with paper mill sludge (Man+PMS) at C/N ratios of 14, 21, and 28 and compared those with the emissions from conventionally treated soil. The mine soil was extremely well drained with 59% coarse fragments. Soil-atmosphere exchange of N₂O and CO₂ was determined using a sampling campaign of ten measurements between 16 June and 14 September 2009 (90days) and 13 measurements between 28 June and 9 November 2010 (134days) using static vented chambers at ambient and increased moisture (water added) content. Potential denitrification was determined in a laboratory incubation experiment. While non-amended mine soil did not have a measurable potential for denitrifying activity, the manure-based amendments introduced the potential. Soil water filled pore space was less than 60% on most sampling days in both ambient and water-added plots. Daily N₂O-N emissions ranged between 40 and 70gNha^-1 with cumulative emissions of 2-4kgNha^-1 from non-amended, lime and fertilizer (L+F) and Comp, and 3-10kgNha^-1 from Man+PMS treatments. The maximum emission obtained from Man+PMS represented <1% loss of applied N. Although stabilized manure-treated soil exhibits the potential for N₂O production, the emission is limited when soils are excessively well drained and reducing conditions rarely develop.